Additive manufacturing (AM), also known as direct digital manufacturing, refers to a wide range of processes for the direct fabrication of final parts, functional prototypes, or both using rapid prototyping technology. In AM, parts are fabricated by deposition using a heat source to locally soften or melt material in order to fuse added material with existing material. In some AM processes (e.g., those based on friction stir welding), the material is heated enough to allow fusion of added and existing material without melting. In other AM processes, the material is melted, and as the heat source is translated across the part being fabricated, a bead is formed consisting of a moving melt pool with solidified material behind it. Material is fed into the heated region (either directly or by other techniques such as via a powder applied to the surface of the part), and the part is built up by multiple passes to form the part shape. AM is used for Free Form Fabrication (F3), which is the rapid manufacture of a complete part, and for additive manufacturing and repair (AMR), which adds one or more features to an existing component, either as a manufacturing step or for component repair. For instance, AM can be used to build parts from titanium alloys, which has applications in the aerospace and medical implant industries.